题解 | #求二叉树的层序遍历#

二叉树的层序遍历有两种方法，分别是递归和队列，我看上面的大佬都用的递归，我来个队列的吧

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param root TreeNode类 
# @return int整型二维数组
#
class Solution:
    def levelOrder(self , root: TreeNode) -> List[List[int]]:
        # write code here
        res = []
        tree_list = []
        if root == None:
            return res
        tree_list.append(root)
        while len(tree_list) > 0:
            level_number = len(tree_list)
            tmp = []
            for i in range(level_number):
              	# 记录每一层的节点个数
                node = tree_list.pop(0)
                tmp.append(node.val)
                if node.left:
                    tree_list.append(node.left)
                if node.right:
                    tree_list.append(node.right)
            res.append(tmp)
        return res